The present invention relates to fluidic pulse generator devices, particularly a backload-responsive fluidic switch having high pressure recovery, and still more particularly to a backload-responsive fluidic switch having high pressure recovery for driving flexible bladders and massaging apparatus.
In PCT international application No. PCT/US00/06702 published May 11, 2000, a crossover-type fluidic switching element of the type shown in FIG. 1 is utilized. In such a construction, the power jet in the interaction region deflects but a fraction of that of the normal oscillating mode (without backloading). So small was this deflection that it was thought that the alternate inflation/deflation of two bladders (one on each of the two receivers) could be accomplished with an ordinary Y- or T-connector. It proved not to be the case. A large model of the crossover-type switching element was tested using water with tracer dye introduced in the power nozzle and again showed unusually small deflections in the interaction region as the receiver flow switches in correspondence to backloading. However, when a normal crossover-type element with two receivers was modified by eliminating or machining away the portion that contained the power nozzle and control channels and most of the interaction area. The remaining fragment of the original silhouette was tested with two bladders with the same result as the original unit with blocked control ports. Thus, it is believed that the major control centers about the bistable nature of the system is in the receiver geometry.
Accordingly, the present invention is directed to a backload-responsive fluidic switch having high pressure recovery. According to the invention, a fluidic switch having a relatively high pressure recovery (greater than 50%) is constituted by a power nozzle, projecting a jet of fluid towards a splitter, the splitter defining a pair of receiver channels or diverging flow paths. The diverging flow paths from the splitter have a common connection with the power nozzle and have respective bounding walls. Each respective bounding wall diverging from the centerline through the power nozzle no more than about 50xc2x0. The splitter defines respective inner walls of the diverging channels or flow paths, with the splitter being spaced a distance of about 3W (W being the width of the power nozzle) from the power nozzle. At least one vent is connected to one of the fluid flow passages.
In one embodiment, an inflatable bladder is connected to one of the diverging fluid flow passages and a vent is connected to the other fluid flow passages. Thus, when a jet of fluid is issued through the power nozzle, the jet of fluid forms a first coanda attachment bubble on the bounding wall leading to the inflatable bladder, thereby increasing the pressure in the bladder and strengthening the coanda attachment bubble. After the first fluid pressure in the bladder reaches a set load or level, the first coanda attachment bubble forces the jet to the switch to the opposite output passage. In the case of a single bladder, the jet is switched to an output leg with its own attachment bubble and a vent. Entrainment in the output leg starts to lower the pressure in the bag enough for the jet to switch back to the output channel having the bladder attached to it and the cycle repeats. In this embodiment, structurally the jet is biased to the output with the bladder attached.
In a second embodiment, a two-bag or bladder version is disclosed. In the two-bag embodiment, the fluidic switch has relatively high pressure recovery (more than 50%) and is constituted by a power nozzle projecting a jet of fluid towards a splitter with the splitter defining a pair of receiver channels. A pair of attachment walls are provided adjacent the power nozzle and a pair of vents is provided adjacent the attachment walls, one vent for each of the respective output channels of the fluidic switch. Thus, switching of the jet of fluid back and forth between the receiver channels is caused when the backload in each receiver channel overcomes the wall attachment at its associated attachment wall. In other words, the operation is similar to the one-bag version except in the one-bag version the biased start-up conditions is provided.
The invention features a backload-responsive fluidic switch having high pressure recovery of more than 50% comprising a body member having a power nozzle having a width W and a centerline CL, said power nozzle being adapted to be coupled to a source of fluid under pressure for issuing a jet of fluid along said centerline, a pair of diverging fluid flow passages having a common connection with the power nozzle and respective bounding walls, each respective bounding wall diverging from the power nozzle centerline no more than about 50xc2x0, and a splitter defining respective inner walls of said pair of diverging walls, said splitter being spaced a distance of about 3W from said throat. An inflatable bladder is connected to one of the diverging fluid flow passages, and a vent connected to the other of the fluid flow passages.
The backload-responsive fluidic switch defined above further features a pair of inflatable bladders, one connected to each of the diverging flow passages, respectively, and, wherein there is a vent connected to each of the fluid flow passages downstream of said power nozzle, the bounding wall portions between said power nozzle and each vent constituting coanda attachment walls, respectively.
Further, on one embodiment of the backload-responsive fluidic switch defined above, the power nozzle centerline is offset or structurally biased relative to the one of said diverging fluid flow passages to which said inflatable bladder is connected.
Still further, the backload-responsive fluidic switch defined above, the vent(s) is connected to the flow passage(s) a selected distance (beyond the coanda bubble, but as close to the bubble as possible, to achieve high pressure recovery) from the power nozzle and the portion of the bounding wall from the power nozzle to said vent constitutes a coanda attachment wall.
Finally, in the backload-responsive fluidic switch defined above, when a jet is issued through the power nozzle, the jet of fluid forms a first coanda attachment bubble on one of the bounding walls leading to an inflatable bladder thereby increasing the pressure in the bladder and strengthening the first coanda attachment bubble, and after the fluid pressure in the bladder reaches a selected level, said attachment bubble begins to get pressurized and the jet is forced to the other of said diverging fluid flow passages.